The purpose of this study is to describe the coordination of mastication, oral food transport and swallowing during intake of solid food in normal human subjects. Although swallowing includes preparatory, oral, and pharyngeal stages, most prior research in humans has focused on the pharyngeal stage as an isolated event. This project focuses on the preparatory and oral stages of swallowing and their relationship during the process of feeding. Specific aims include determining how motions of the hyoid bone and tongue are coordinated with jaw motion cycles (gape cycles) during food intake, and describing how varying the physical characteristics of the food affects oral transport and swallowing. Other specific aims are to determine how instructing subjects to swallow on command alters the coordination of the preparatory, oral, and pharyngeal stages; and discerning whether the oral transport mechanism is dependent on gravity. Simultaneous videofluorography and electromyography will be performed on subjects eating a variety of radiopaque foods. Each subject will begin by sitting upright and eating in a spontaneous manner, while images are recorded in the lateral projection. A subgroup will repeat the protocol during postero-anterior imaging. Another sub-group will eat each food a second time with instructions to chew the food, hold it in the mouth, and swallow on command. A third sub-group will repeat the protocol lying prone, to study the effect of gravity. Videofluorographic and electromyographic data will be digitized and acquired by a computer. The progression of the bolus through the foodway and the overall movement patterns of the jaw, hyoid bone, and tongue will be evaluated by reviewing the videotapes in slow motion, one frame at a time. Graphs will be constructed to show myoelectric activity and motion of the jaw and hyoid bone over time. Temporal relationships among jaw motion, byoid motion, tongue shape, and muscle activity will be quantified using a variety of statistical techniques. This project will provide important new understanding of the basic motor control mechanisms underlying mastication and swallowing.